If a woman mis-carries she becomes emotionally drained. She looks as if she hasn't slept in a while.If you are wondering how you can tell if you mis-carried, you should see your physician or a doctor.
Well there is no way of really telling. The best way to know is to ask. But that could scare him/her off. You can bring it up in conversation if you want and casually ask. Don't be blunt about it...